1. Field of the Invention
Embodiments of the present invention relate to an organic light emitting display and a driving method thereof. More particularly, embodiments of the present invention relate to an organic light emitting display and a method for driving the same, which is applicable to a digital drive.
2. Description of the Related Art
Recently, various flat panel displays having reduced weight and volume compared with cathode ray tubes (CRT) have been developed. Flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays.
Organic light emitting displays make use of organic light emitting diodes (OLEDs) that emit light by re-combining electrons and holes. The organic light emitting display may provide high response speed and small power consumption.
The OLED generates light of a predetermined luminance corresponding to a current from a pixel circuit receiving power from a first power supply. Typically, an anode of the OLED is coupled to the pixel circuit and a cathode thereof is coupled to a second power supply. To control the current, the pixel circuit typically includes a transistor between the first power supply and the OLED, and a storage capacitor between a gate electrode and a first electrode of the transistor.
Thus, pixels of the conventional organic light emitting display express gradations using a voltage stored in the storage capacitor. However, exact expression of desired gradations may not be realized. In practice, it may be difficult to accurately express a brightness difference between adjacent gradations using analog driving noted above.
Further, transistors in the pixel circuits may have differing threshold voltages and electron mobilities due to a process deviation. Thus, the pixels may generate light of different gradations with respect to the same gradation voltage, resulting in non-uniform luminance.